The very talented Griffin Stuip (Griph010 on Flickr) took these photos on an Olympus Trip 35, using a film expired in 1999, and has achieved great photographs as a result!
You can get some great results by using expired film. These photos were all taken on my Olympus Trip 35, using a variety of films expired between 2009-10. If you can get your hands on older films you can get more distorted photos, but they're difficult to find for a reasonable price. I've bought all of mine from ebay.